In recent years, as recording mediums, the market of disk-like recording mediums has expanded with an advantage of a high access speed. Under the present circumstances, it has been necessary to improve an access speed by achieving a high-speed winding speed of a tape in equipment such as a video tape recorder, which uses a tape-like magnetic recording medium (hereinafter, referred to as a tape) as a recording medium. Hence, motors for driving reels for winding tapes have increased in rotation speed and reduced in fast forwarding time and rewinding time to improve usability.
FIG. 5 shows a conventional tape-like recording medium running device and a configuration required to achieve an operation for making a transition from fast forwarding (FF)/rewinding (REW) modes to a stop mode of a tape. Such a tape-like recording medium running device is disclosed in Japanese Unexamined Patent Publication No. 04-48460 and so on.
In FIG. 5, a tape 22 has a leading edge which is connected and wound by a supply reel 3 and a trailing edge which is connected to a take-up reel 2.
Reference numeral 2A denotes a take-up reel base engaged with the set take-up reel 2. Reference numeral 3A denotes a supply reel base engaged with the set supply reel 3.
Reference numeral 1 denotes a motor which transmits rotation to a take-up side reel of the take-up reel base 2A and the supply reel base 3A via a belt and a gear to rotationally drive the take-up side reel. To be specific, in the case of the fast forwarding (FF) mode in which the tape 22 wound around the supply reel 3 is wound up by the take-up reel 2 at high speed, the motor 1 rotationally drives the take-up reel base 2A of the take-up reel 2 serving as a take-up side reel. In the case of the rewinding (REW) mode in which the tape 22 wound around the take-up reel 2 is wound up by the supply reel 3 at high speed, the motor 1 rotationally drives the supply reel base 3A of the supply reel 3 serving as a take-up side reel.
Reference numeral 5 denotes a take-up reel braking unit which brakes the rotation of the take-up reel base 2A.
Reference numeral 6 denotes a supply reel braking unit which brakes the rotation of the supply reel base 3A.
Reference numeral 50 denotes a stop command detecting unit which detects that an operating unit 23 is operated to make a stop from the fast forwarding (FF) or the rewinding (REW) mode and produces first and second stop commands 50A and 50B.
Reference numeral 8 denotes a mode changing unit which makes a change to the stop mode by operating the take-up reel braking unit 5 and the supply reel braking unit 6 in accordance with the fast forwarding (FF)/rewinding (REW) modes to apply braking forces to the take-up reel base 2A and the supply reel base 3A when the first stop command 50a is detected.
Reference numeral 4 denotes a rotation detecting unit which has an MR element (magneto-resistance element) for detecting polarities (north pole and south pole) magnetized at predetermined intervals around the motor 1 and for outputting a frequency signal. The rotation detecting unit outputs a signal of a frequency proportionate to a rotation speed of the motor 1.
Reference numeral 51 denotes a speed control unit which operates the motor 1 via a driving unit 52 so that the output of the rotation detecting unit 4 comes close to a target number of rotations corresponding to an operation mode instructed by the operating unit 23, to be specific, a target number of rotations corresponding to the fast forwarding (FF)/rewinding (REW) modes until the second stop command 50B is detected. When the second stop command 50B is detected, the rotation of the motor 1 is stopped.
The following will discuss operations of the conventional tape-like recording medium running device configured thus.
First, in the fast forwarding (FF) mode, a rotation command to wind up the tape 2 at high speed (e.g., 8 m/s) is outputted by the speed control unit 51 and the motor 1 is operated via the driving unit 52. Namely, as shown in FIG. 6(a), current of a predetermined value C is applied to the motor 1 and the rotation is controlled according to the current value.
The take-up reel 2 where rotation is transmitted via the rotation of the motor 1 winds up the tape 22 from the supply reel 3.
When the operating unit 23 is operated to provide a command to stop a forwarding operation at timing T1, this command is detected by the stop command detecting unit 50. In the speed control unit 51, a command to stop the rotation of the motor 1 is outputted, current applied to the motor 1 is changed to 0 from the predetermined current value C, and the motor 1 is rotated only by inertial force thereafter.
When the command to stop the fast forwarding (FF) mode is provided at the timing T1, in the mode changing unit 8, a mechanism is changed from the fast forwarding mode to the stop mode. As shown in FIGS. 6(b) and 6(c), when it is assumed that the reel braking unit 5 has braking force of BT1 and the supply reel braking unit 6 has braking force of BS1, it is necessary to satisfy the following relationship:BT1<BS1so that the take-up reel 2 is prevented from stopping earlier than the supply reel 3 and the supply reel is pulled and rotated by the take-up reel 2.
This is because when the take-up reel 2 is stopped earlier than the supply reel 3, the tape 22 sent by the rotation of the supply reel 3 cannot be wound by the take-up reel 2 and a slack appears on the tape 22, resulting in a damage on the tape 22 in the subsequent running of the tape.